(a) Field of the Invention
The present invention relates to a mold for hot stamping and a method of manufacturing the same. More particularly, the present invention relates to a mold for hot stamping and a method of manufacturing the same that can improve cooling speed and cooling performance by flowing coolant smoothly during hot stamping where a super high strength product is manufactured at a high temperature.
(b) Description of the Related Art
Generally, molds are divided into injection molds for manufacturing plastic products, press molds for manufacturing products by using steel plates, and die casting molds for manufacturing products by melting metals and injecting the molten metal into the die casting molds. Typically, such molds include a movable mold and a fixed mold so as to manufacture the products without a hitch. Particularly, as use of the molds for manufacturing the products used in a vehicle increases, the molds as well as the products must technologically progress with new design needs.
Recently, improving collision performance and securing safety have become one of the main concerns of the vehicle manufacturing industry. As a result, vehicle manufacturing companies have begun to use transformation induced plasticity (TRIP) steel, dual phase (DP) steel, aluminum alloy steel, and magnesium alloy steel or conduct investigation into new technologies such as tailed welding blank (TWB), hydroforming, hot stamping so on to lighten and strengthen a vehicle body.
Herein, the hot stamping is a process for forming a panel at a high temperature to lighten the weight and to maintain strength of the vehicle body during manufacturing. After a material is heated to the high temperature, the material is pressed and a mold itself is cooled to manufacture high strength products according to the hot stamping.
The hot stamping process includes heating a blank to a temperature greater than an Ac3 transformation point so as to austenitize the blank completely. The blank is formed and quickly cooled in the mold to transform the blank into high strength martensite.
The components of the vehicle body manufactured by the hot stamping have tensile strength greater than or equal to 1500 MPa. Therefore, collision performance of the vehicle may be improved and a high degree of safety may be provided to its occupants.
In order to supply coolant into the mold used in a conventional hot stamping process, coolant apertures configured to receive the flow the coolant are directly formed at the mold. In this configuration, however, it is very difficult to form the coolant apertures in the mold for manufacturing products of complex shapes and thus a large amount time is necessary for forming these coolant apertures in the mold.
When a number of the coolant apertures are formed in the mold to cool the mold quickly, the strength of the mold may be deteriorated in the conventional hot stamping method. Therefore, cracks or damage may occur in the mold due to contraction or deformation of the mold when the temperature of the mold changes quickly. Thus, the coolant flowing in the mold may as a result leak.
Since design, manufacture, and verification of coolant flow lines in the mold is achieved based on an actual model, initial investment and time for developing the products may increase. Therefore, an optimal cooling method for the mold should be developed at a design step of new products.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.